jQuery - Sticky header that shrinks when scrolling down

Question

I wonder how to make a sticky header shrink(with animation) when you scroll down the page and goes back to normal state when the page is scrolled up to the top. Here are two

Answer 1

Based on twitter scroll trouble (http://ejohn.org/blog/learning-from-twitter/).

Here is my solution, throttling the js scroll event (usefull for mobile devices)

JS:

$(function() {
    var $document, didScroll, offset;
    offset = $('.menu').position().top;
    $document = $(document);
    didScroll = false;
    $(window).on('scroll touchmove', function() {
      return didScroll = true;
    });
    return setInterval(function() {
      if (didScroll) {
        $('.menu').toggleClass('fixed', $document.scrollTop() > offset);
        return didScroll = false;
      }
    }, 250);
  });

CSS:

.menu {
  background: pink;
  top: 5px;
}

.fixed {
  width: 100%;
  position: fixed;
  top: 0;
}

HTML:

MENU FIXED ON TOP

http://codepen.io/anon/pen/BgqHw